Description document for a service offered by a server in a communication network and method of validating a multimedia document

ABSTRACT

A description document for a service offered by a server in a communication network comprises a first abstract part adapted to describe at least one message exchanged on the communication network when a service is implemented and a second concrete part adapted to describe the information relating to the transmission of the messages over the communication network. This service description document comprises, in the first abstract part, a description of abstract constraints associated with a binary multimedia document. It has particular use for validating a multimedia document from the extraction (E 11 ) of the description of abstract constraints and the extraction (E 12 ) of the MPEG7 description of this multimedia document.

The present invention concerns a document describing a service offeredby a server in a communication network.

It also concerns a method of making a request for a service offered by aserver in a communication network.

Finally, it concerns a method of validating a multimedia documentinserted in a message intended to be exchanged over the communicationnetwork when a service offered by a server in the communication networkis implemented.

Within a computer communication network like the Internet, servercomputers are offering services to other computers, referred to asclient computers, more and more.

In practice, the client computer sends a message comprising data to theserver computer, which processes these data and returns a result.

Such services are referred to as Web services.

Because of the increase in these services available on a communicationnetwork, the protocols for data exchange between computers arefrequently standardized.

Thus the SOAP protocol is a protocol for exchanging structuredinformation over the Internet.

According to this SOAP protocol, the information exchanged is structuredby means of XML (extended Mark-up Language) tags.

SOAP is a communication protocol which thus makes it possible to accessremote services.

This SOAP standard defines the general structure of the messagesexchanged as well as the processing which has to be performed by acomputer sending or receiving SOAP messages.

A SOAP message is composed of one or more blocks, distributed in twomajor categories: header blocks, encapsulated in a tag <header>, andbody blocks, encapsulated in a tag <body>.

In addition, a SOAP message is transmitted from one computer to anotherover the communication network by means of a communication protocol suchas HTTP (Hyper Text Transfer Protocol), SMTP (Simple Mail TransferProtocol), the protocol used for the exchange of electronic mail, or theFTP protocol (File Transfer Protocol), the protocol used for thetransfer of files.

The layer which makes it possible to interface SOAP with these variouscommunication protocols is referred to as a “binding”.

The SOAP application makes it possible to transport binary data, such asimages, via a “SOAP+Attachment” extension which can use mechanisms suchas MIME or DIME.

There is also known a computer service description language WSDL (WebService Description Language) which describes Internet services, and inparticular services defined by the SOAP standard.

A WSDL document thus contains a list of the services offered by a servercomputer in a communication network.

This WSDL language is itself an application of the XML mark-up language.

A description of the WSDL 1.1 language will be found on the computersite at the address http://www.w3.org/TR/2001/NOTE-wsdl-20010315.

In practice, an electronic document describing a service in WSDLlanguage comprises two parts.

A first part, referred to as the “abstract part”, is adapted to describethe messages exchanged between computers in the communication networkwhen a service is being supplied.

In particular, this first part makes it possible to define the type ofdata exchanged, and the type of messages used during the execution ofthe service, as well as the operations implemented, defined by themessages which are exchanged when the service is executed.

An operation can therefore be seen as an elementary service, itselfimplemented by one or more messages in accordance with a logicalsequence of message organization.

The description document of a WSDL service also comprises a second partadapted to define information relating to the transmission of themessages over the communication network.

It indicates in particular how the messages are encoded in order to betransmitted over the network and which communication protocol isactually used.

The current representation of a WSDL document represents in asatisfactory manner the services offered by a server in thecommunication network handling XML data. This is because, in this case,a description document of a WSDL service enables a server in thecommunication network to describe abstractly the XML data exchanged byvirtue of XML schemas defined in the section “[type/]” of the WSDLdescription.

According to the WSDL 1.1 standard, a WSDL service description documenttheoretically makes it possible to describe message exchanges comprisingbinary data, such as images, by virtue of the MIME extension.

The following example illustrates the syntax used: <wsdl:types>   ... </wsdl:types>  <message name=“giveImageMsg1”>   <part name=“image”type=“xsd:binary”/>   <part name=“directory” type=“tns:DirectoryType”/> </message>  <portType name=“ImageManipulations”>   <operationname=“addImage”>     <input message=“giveImageMsg” name=“imageInput”>  </operation>  </portType>  <binding>   <operation name=“addImage”>    <soap:operation name=“http://example.com/addImage”/>     <input>      <mime:multipartRelated>         <mime:part>           <soap:bodyparts=“directory” use=“litteral”/>         </mime:part>        <mime:part>           <mime:content part=“image”type=“image/gif”/>         </mime:part>       </mime:multipartRelated>    </input>   </operation> </binding>

It is thus found that, in the abstract definition part of the message“giveImageMsg1”, this message is defined as the combination of twoparts: a first “image” part corresponding to an image; and a second“directory” part corresponding to XML data.

A type “xsd:binary” is given to the “image” part. However, this type isrelated to the serialization used and does not have any true meaning: itis a case in fact of a table of binary values.

In the second part of the WSDL document, this message is serialized atthe protocol level in the form of a “multipart” MIME message, the firstpart of which corresponds to the XML data, and the second part to theimage.

This second part takes the form of a MIME attachment of the type“image/gif”.

Thus, when a server and a client in the communication network wish toexchange multimedia contents, such as images, apart from any XML data,the WSDL service description document does not make it possible todescribe these multimedia contents abstractly.

A WSDL service description document only makes it possible to describethe exchange of multimedia data via the “mime” extension. This extensionsolely defines the transmission format of the multimedia content, givingthe “mime” type of the document such as: image/jpeg, video/mjpeg4 etc.

The purpose of the present invention is to resolve the aforementioneddrawbacks and to propose a service description document giving thepossibility of making descriptions of a multimedia content, in the sameway as XML data.

To this end, the present invention relates, according to a first aspect,to a document describing a service offered by a server in thecommunication network comprising a first abstract part adapted todescribe at least one message exchanged over the communication networkwhen a service is implemented and a second concrete part adapted todescribe the information relating to the transmission of the messagesover the communication network.

According to the invention, this service description document comprises,in the first abstract part, a description of abstract constraintsassociated with a binary multimedia document.

Thus the service description document does not directly describe themultimedia content, in the form of a table of binary values, butcomprises a description of constraints associated with this document.

This description of abstract constraints makes it possible to definevarious constraints applicable to a multimedia document, such as forexample a maximum image size in terms of number of pixels.

It is thus possible in the abstract part of the document to define amessage including a reference to this description of abstractconstraints.

Such a message is thus adapted to contain a binary multimedia document,provided that the document meets the abstract constraints described inthe service description document.

According to a preferred characteristic of the invention, thedescription of abstract constraints is represented using the semanticsof a language describing a content of a binary multimedia document.

It is in fact advantageous to use semantics already accessible anddefined to describe the content of a binary multimedia document.

In a preferred embodiment of the invention, this description of abstractconstraints is represented using the semantics defined by the MPEG7standard.

This is because this MPEG7 standard is a multimedia content descriptionstandard, this standard being flexible and capable of extension.

The descriptors and, description schemas according to the MPEG7 standardare adapted to describe multimedia contents. In practice, a descriptortakes a multimedia document as an input and generates an XML document.This XML document respects the syntax defined by the associated MPEG7description schema and gives the characteristics of the multimediadocument vis-à-vis the chosen descriptor.

It is thus possible to use this description of the multimedia documentaccording to the MPEG7 standard to include it in a description documentof a service according to the invention, in order to describe abstractconstraints associated with the multimedia document.

In practice, the description of abstract constraints is inserted in asub-part of the first abstract part adapted to describe an abstractstructure of the messages exchanged.

This description of abstract constraints can thus be used in the sameway as in the case of XML data, defined in a “specimen” sub-part of thefirst abstract part of the description document of a service.

This first abstract part also comprises a second sub-part adapted todeclare at least one elementary message pointing to the description ofabstract constraints.

According to a second aspect of the invention, it concerns a method ofproducing a request for a service offered by a server in a communicationnetwork, the service being described in the description document of aservice in accordance with the invention.

This method of producing a request comprises the following steps:

-   -   reading the description document of a service;    -   selecting a first abstract part adapted to describe at least one        message exchanged over the communication network when an        operation associated with the service is implemented;    -   extracting a description of abstract constraints associated with        a binary multimedia document;    -   selecting a binary multimedia document according to the        description of abstract constraints; and    -   producing a request intended for the server in the communication        network including the binary multimedia document selected.

By virtue of the description document of a service according to theinvention, it is possible to produce a request integrating a binarymultimedia document selected according to the description of abstractconstraints inserted in the description document of a service.

It is thus possible to produce a request on a communication networkallowing the exchange of multimedia data from constraints defined by aserver via a description document of a service.

According to a third aspect of the invention, it concerns a method ofvalidating a multimedia document inserted in a message intended to beexchanged over the communication network when a service offered by aserver in this network is implemented, the service being associated witha service description document.

According to the invention, this validation method comprises thefollowing steps:

-   -   extracting the multimedia document inserted in the message;    -   extracting a description of abstract constraints associated with        a binary multimedia document from the description document of a        service;    -   extracting a content description associated with the multimedia        document; and    -   comparing the content description and the description of        abstract constraints extracted from the service description        document.

The description document of a service according to the invention is thusused for validating a message before or after its transfer over thecommunication network, according to its description.

By virtue of the invention, a message may be validated not only withregard to the content of the XML data, but also with regard to thecontent of the binary data, associated with a multimedia document.

According to a preferred characteristic of the invention, thisvalidation method is used during a step of selecting a multimediadocument to be inserted in a message exchanged at the time of theimplementation of a service offered by a communication server.

This validation method can thus be implemented with regard to a clientcomputer, when a request including one or more messages intended for theserver is produced. It makes it possible to ensure that the multimediadocument addressed to the server can actually be used by this server forimplementing the service offered.

At the same time, this validation method according to the invention canalso be implemented at the time of the validation of a request receivedby a server in a communication network for implementing a servicedescribed in a service description document.

Thus it is possible, at a server in the communication network, tovalidate a request including one or more messages having a multimediacontent, before the execution of the service and the use in particularof this multimedia content.

The present invention also concerns a device for producing a request fora service proposed by a server of a communication network, the servicebeing described in a service description document according to theinvention.

This device for producing a request comprises:

-   -   means for reading the description document of a service;    -   means for selecting a first abstract part adapted to describe at        least one message exchanged over the communication network when        an operation associated with the service is implemented;    -   means for extracting a description of abstract constraints        associated with a binary multimedia document;    -   means for selecting a binary multimedia document according to        the description of abstract constraints; and    -   means for producing a request intended for the server in the        communication network including the binary multimedia document        selected.

It also concerns a device for validating a multimedia document insertedin a message intended to be exchanged over the communication networkwhen a service offered by a server in the communication network isimplemented, the service being associated with a service descriptiondocument.

This validation device comprises:

-   -   means for extracting the multimedia document inserted in the        message;    -   means for extracting a description of abstract constraints        associated with a binary multimedia document from the        description document of a service;    -   means for extracting a content description associated with the        multimedia document; and    -   means for comparing the content description and the description        of abstract constraints extracted from the service description        document.

These devices for producing a request and validating a multimediadocument have characteristics and advantages similar to those of themethods which they implement.

The present invention also concerns a server computer in a communicationnetwork comprising means adapted to implement a validation methodaccording to the invention.

It also concerns a client computer in a communication network comprisingmeans adapted to implement the method of producing a request for aservice in accordance with the invention and the validation methodaccording to the invention.

More generally, the present invention concerns a communication networkadapted to implement the methods described above according to thevarious aspects of the invention.

It also concerns an information storage means, possibly totally orpartially removable, which can be read by a computer system, comprisinginstructions for a computer program adapted to implement the methodsdescribed above according to the various aspects of the presentinvention, when this program is loaded in and run by the computersystem.

Finally, it concerns a computer program which can be read by amicroprocessor, comprising portions of software code adapted toimplement the methods described above according to the various aspectsof the present invention, when this computer program is loaded in andrun by the microprocessor.

Said server computer, client computer, communication network,information storage means and computer program have characteristics andadvantages similar to those of the methods which they implement.

Other particularities and advantages of the invention will also emergefrom the following description.

In the accompanying drawings given by way of non-limiting example:

FIG. 1 is an algorithm illustrating the validation method according toone embodiment of the invention;

FIG. 2 is an algorithm illustrating the method of producing a requestfor a service according to one embodiment of the invention;

FIG. 3 is an algorithm illustrating the execution of a request for aservice received by a server in a communication network; and

FIG. 4 is a block diagram illustrating a computer adapted to implementthe invention.

A description will first of all be given of the structure of a servicedescription document according to a first aspect of the invention.

The case is adopted in which a client computer C and a server computer Sin a communication network wish to exchange multimedia contents, inaddition to any XML data.

Description documents of a WSDL service are already known giving thepossibility of describing types of messages exchanged on thecommunication network when these messages comprise XML data.

The description document of a service according to the invention offersthe possibility of making a specimen description of multimedia documentssuch as for XML data.

A description document of a WSDL service comprises a first abstract partadapted to describe the messages exchanged on the communication networkwhen the service is implemented and a second concrete part adapted todescribe the information relating to the transmission of the messages onthe communication network.

In accordance with the invention, the improved service descriptiondocument comprises in the abstract part a description of abstractconstraints associated with a binary multimedia document.

Thus the service description document does not directly comprise themultimedia data, in the form of binary values, but a description ofthese documents and constraints applied to this document.

It is thus possible to make a specimen description of multimediadocuments, in the same way as for XML data.

This specimen description of multimedia documents can comprise thefollowing constraints:

Image whose size is a maximum of 640×480 pixels;

Image solely in grayscale;

Video sequence of the “title” film;

Music composed by “author”;

Multimedia document comprising in its header data the name of itscreator, etc.

The description of abstract constraints is preferably represented usingthe semantics of a description language of a content of a binarymultimedia document.

It is thus possible to use a known description language, and preferablya description language using a mark-up language of the XML type.

In the remainder of the description, the semantic defined by the MPEG7standard is considered.

This MPEG7 standard is a flexible and extendable multimedia contentdescription standard. It defines a set of methods and tools for thevarious phases of the description of multimedia documents.

The MPEG7 standard can be separated into three parts:

-   -   the MPEG7 descriptors;    -   the MPEG7 description schemas; and    -   a descriptor definition language.

The MPEG7 descriptors and description schemas make it possible todescribe multimedia contents.

In practice, a descriptor considers a multimedia document as an inputand as an output generates an XML document. This document, in XMLmark-up language, complies with the syntax defined by the MPEG7description schema associated with the document.

It gives the characteristics of the multimedia document vis-à-vis thechosen descriptor.

The descriptor definition language allows integration of new descriptorsto MPEG7 by the construction of new description schemas.

An example of an MPEG7 description of an image in grayscale and with asize of 365×452 pixels is given below: <Mpeg7xmlns=“urn:mpeg:mpeg7:schema:2001”   xmlns:xsi=“http://www.w3.org/2001/XMLSchema- instance”   xmlns:mpeg7=“urn:mpeg:mpeg7:schema.2001”   xsi:schemaLocation=“urn:mpeg:mpeg7:schema:2001 Mpeg7-2001.xsd” > <Description>   <MultimediaContent>    <Image>     <MediaInformation>     <MediaProfile>       <interleave>       <VisualCoding>       <interleave>          <Format           href=urn:mpeg:...:VisualCodingFormatCS:2001:1”          colorDomain=“grayscale”/>          <Frame width=“356”height=“452”/>         </interleave>        </VisualCoding>      </interleave>      </MediaProfile>     </MediaInformation>   </Image>   </MultimediaContent>  </Description> </Mpeg7>

According to the present invention, a description is given in theservice description document not directly the multimedia content but theMPEG7 document corresponding to this content.

In practice, this description of abstract constraints is inserted in asub-part of the first abstract part of the service description document,this sub-part being adapted to describe an abstract structure of themessages exchanged.

This description of abstract constraints is thus placed inside the tag[wsdl:types] of the service description document.

It is thus possible to describe multimedia document types in a similarmanner to the XML-Schema language used for XML data.

The advantage of reusing the semantics of the MPEG7 standard lies in thefact that this standard is very complete, well known and well understoodon the communication network and supported by many validation tools.

In addition, a description according to the MPEG7 standard can beincluded directly in a multimedia document. Access to this MPEG7description is simplified since this multimedia document is possessed.

An MPEG7 document is a document representing an XML mark-up languagewhich can also be described by means of XML schemas.

In order to describe a multimedia content, it is necessary to describethe MPEG7 description type which the multimedia document can take.

In practice, an XML schema is written, the MPEG7 description associatedwith an image being validated or not with regard to this XML schema.

It should be noted that it is possible to obtain several MPEG7descriptions for the same multimedia document, since many imagecharacteristic extraction tools exist and an MPEG7 description caninclude several of these or include various items of informationthereon.

The description of abstract constraints inserted in the servicedescription document according to the invention must therefore describethe minimum set of constraints which an MPEG7 description must meet.

In this regard, according to a first embodiment of the invention, thedescription of abstract constraints is represented in a schema languagesuch as “Schematron”. This language is adapted to define a set ofminimum constraints.

It is thus possible to define a sufficiently flexible schema to give aset of minimum constraints without obliging the multimedia document tocontain only this set.

The “Schematron” language defines a set of laws: a law links one or moreXML nodes (specified by XPath), a Boolean test and a result.

Although less well known than the XML-Schema and Relax-NG schemalanguages, the Schematron language allows direct validation of amultimedia document from the point of view of the abstract constraintsthus defined by this language.

An example of a description of a multimedia content by means of thisSchematron language within an element “wsdl:type” of a servicedescription document is given below: <wsdl:types>  <sch:schemaxmlns:sch=“http://www.ascc.net/xml/schematron”>   <sch:patternname=“MyImageType”>    <sch:rule context=“Mpeg7”>     <sch:asserttest=“count(Description)&gt; 1”/>    </sch:rule>    <sch:rulecontext=“Mpeg7/Description”>     <sch:assert test=“count(Collection) =1”/>    </sch:rule>    ...    <sch:rule context=“Mpeg7/.../Frame”>    <sch:assert test=“@width &gt; 0 and @width &lt; 640”/>   </sch:rule>    <sch:rule context=“Mpeg7/.../ Format ”>    <sch:assert test=“@colorDomain =‘grayscale’”/>    </sch:rule>    ...  </sch:pattern>  </sch:schema> </wsdl:types>

According to a second embodiment of the invention, the description, ofabstract constraints is represented in the service description documentin a schema language such as XML-Schema or Relax-NG, the tags beingdefined using the semantics of the MPEG7 standard.

The use of these XML-Schema or Relax-NG languages has the advantage ofmaking it possible to easily define the tree of an XML document.

In this tree, the abstract constraints to be defined may concern only anXML sub-tree of the complete XML document.

By way of non-limiting example, it is possible for example to constrainsolely the width of an image and not its height.

The MPEG7 standard defines two attributes “width” and “height” for anelement “image”.

The description document of a service will preferably define only theattribute “width” for the element “image” since the attribute “height”has no constraints.

This description can be presented in the following manner: <wsdl:types> <grammar xmlns=“http://relaxng.org/ns/structure/1.0”>   <definename=“MyFrameType”>    <element name=“Frame”>     <attributename=“width”>      <data type=“tns:MySizeType”>       <paramname=“maxInclusive”>640</param>       <paramname=“minExclusive”>0</param>      </data>     </attribute>   </element>   </define>   <define name=“MyImageType”>    <elementname=“Mpeg7”>     ...     <element name=“VisualCoding”>     <interleave>       <element name=“Format”>        <attributename=“colorDomain”>         <value>grayscale</value>        </attribute>      </element>       <ref name=“MyFrameType”/>      </interleave>    </element>     ...    </element>   </define>  </grammar></wsdl:types>

The use of such a syntax makes it necessary to define a specificvalidation tool, when it is sought to validate a multimedia content withregard to the description of a service according to the invention.

In particular, it is necessary to create an extended validation tool forvalidating a document by a schema if one of these sub-trees is validatedin the conventional sense.

This extended validation tool may be implemented in various ways.

A first solution consists of implementing an XSLT transformation whichtransforms the schema as described above into a schema such asSchematron adapted to define minimum constraints.

This XSLT transformation would add to the initial schema elements formaking the schema open and allowing the validation of a multimediadocument with regard to the description of abstract constraints.

A second solution is based on the use of a standard XML validation toolas defined below: Do  RES = Validation(document, schema)  If (RES doesnot contain any error) Test = 1  Otherwise Test = −1  If (RES containsan error of the type ‘element X not defined’)   Remove element X andTest = 0  If (RES contains an error of the type ‘attribute Y notdefined’)   Remove attribute Y and Test = 0 As long as (Test = 0) If(Test = 1) Validation succeeded Otherwise Validation failed

The advantage of using a schema language such as XML-Schema or Relax-NGis using descriptions of multimedia contents and XML data which arerelatively similar.

A third solution consists of representing the description of theabstract constraints in a description language for a content of amultimedia document, and preferably according to the MPEG7 standard.

The tags are then adapted to integrate directly or by referenceattributes represented in a schema mark-up language such as XML-Schema.

Use is then made directly of the elements and attributes defined by theMPEG7 standard within the service description document.

If necessary, the XML-Schema language is used either via an attribute ofthe type “mpeg:type” or directly integrated in the MPEG7 elements.

The following example illustrates the use of the MPEG7 semantics in thisthird solution: <xs:complexType name=“myFrameType”>  <xs:elementname=“Frame”>   <xs:complexType>     <xs:attribute name=“width”>     <xs:simpleType>      <xsd:restriction base=“xsd:integer”>       <xsd:maxInclusive value=“640”/>        <xsd:minExclusivevalue=“0”/>       </xsd:restriction>      </xsd:simpleType>    </xs:attribute>   </xs:complexType>   </xs:element></xs:complexType> <Mpeg7 mpeg:name=“MyImageType”>  <Description> ...   <VisualCoding>     <interleave>       <xs:choice>       <FormatcolorDomain=“grayScale”/>       <Frame mpeg:type=“tns:myFrameType”/>      </xs:choice>     </interleave>    </VisualCoding>  ...</Description> </Mpeg7>

The advantage of this third solution is to present a syntax which isclose to MPEG7 and very readable.

It is then necessary to use a specific validation tool, as before. It isalso possible to use an XSLT transformation document in order totransform the XML syntax into a schema language such as Schematronallowing the direct use of standard validation tools, as before.

Once this description repeating the MPEG7 standards is inserted in the“type” section of the service description document, a reference to thisdescription is inserted in the first abstract part of the servicedescription document.

Conventionally, this first abstract part comprises a second “message”sub-part adapted to declare the elementary messages exchanged during theimplementation of the message.

In this second sub-part, there exists at least one elementary messagepointing towards the description of abstract constraints.

This elementary message is preferably associated with an attributeadapted to specify whether the message comprises a binary multimediacontent type.

An example is given below of a service description document according tothe invention: <wsdl:types>   <grammarxmlns=“http://relaxng.org/ns/structure/1.0”>     <definename=“MyImageType”>    ...</define>   </grammar>  </wsdl:types> <message name=“giveImageMsg1”>    <part name=“image”type=“tns:MyImageType” mpeg:multimedia=“true”/>    <partname=“directory” type=“tns:DirectoryType”/>  </message>  <portTypename=“ImageManipulations”>    <operation name=“addImage”>       <inputmessage=“tnsgiveImageMsg/” name=“imageInput”>    </operation> </portType>  <binding>    <operation name=“addImage”>      <soap:operation name=“http://example.com/addImage”/>       <input>        <mime:multipartRelated>           <mime:part>            <soap:body parts=“directory” use=“litteral”/>          </mime:part>           <mime:part>             <mime:contentpart=“image” type=“image/jpeg”/>           </mime:part>        </mime:multipartRelated>       </input>    </operation> </binding>

In this example, two types of data are defined “MyImageType” and“DirectoryType”. These two types are referenced in the structure of themessage of the operation “addImage”.

This message thus consists of two abstract parts. The first part definesXML data and points to the schema “DirectoryType”. This is theconventional mechanism defined by the WSDL standard.

The second part defines a multimedia content and points to the schema“MyImageType”. The distinction in content type, between XML data ormultimedia content, can be made in two ways:

-   -   either the schema pointed to makes explicit the fact that it        describes solely multimedia contents. Consequently the part        which points to this schema corresponds to a multimedia content.    -   or the service description document clearly makes explicit the        fact that this part of the message is a multimedia content, for        example via an attribute “mpeg:multimedia=“true””, or an        attribute of the mine type specifying that it is a case of a        multimedia document.

This message description thus forms part of a description of an exchangeof messages between a client computer C and a server computer S.

The second concrete part of the service description document, delimitedby a “binding” tag, comprises serialization information.

It is then possible to use conventional mechanisms such as DIME or MIME.

This second concrete part adds the information necessary for sending themessage over the network.

In the previous example, the extension MIME of the WSDL standard isused. The image which will pass over the network is therefore defined inan abstract manner by the schema “MylmageType” and serialized in theform of a MIME attachment.

Such a service description document thus makes it possible to describe amultimedia content in an abstract manner, in a similar manner to what isknown for XML data.

It is then possible to use similar mechanisms of validation of amultimedia document, production and execution of a service request on acommunication network.

A description will be given below with reference to FIG. 1 of a methodof validating a multimedia document intended to be exchanged over thecommunication network when a service is used, when the service isassociated with a service description document according to theinvention.

An acquisition step E10 is first of all implemented in order to acquirea multimedia document.

When a message is produced, for example by a client computer C, thisacquisition step E10 can consist of selecting a multimedia document tobe inserted in a message which will be exchanged when the serviceoffered by the communication server is implemented.

This acquisition can be made using an image database for example.

At the time of validation of a message received, for example by a servercomputer S, this acquisition step E10 consists of extracting themultimedia document from a message exchanged over the communicationnetwork.

An extraction step E11 is then adapted to extract the description ofabstract constraints inserted in the service description document andconnected to the multimedia document acquired at the previous step.

A second extraction step E12 is also adapted to extract the MPEG7description associated with the multimedia document acquired.

It is necessary for the computer implementing this validation method topossess the various MPEG7 extractors adapted to consider a multimediacontent as an input and to give as an output an MPEG7 description.

These extractors can be dedicated to a specific description of amultimedia document (extraction. of the dominant color of an image forexample). It may also be a question of a program which will extract anMPEG7 (binary) description already contained in the multimedia document.

A comparison step E13 next makes it possible to compare this MPEG7description with the description extracted from the description documentof a service according to the invention.

It should be noted that the MPEG7 standard is an extendable standard,and it is not possible to generate a document comprising all thepossible MPEG7 descriptions of the multimedia document.

Several solutions are then possible for implementing this validationmethod.

First of all, it is possible that the computer implementing thisvalidation method supports only a subset of the MPEG7 standard and isthus adapted to generate all the MPEG7 information in this subset in adocument in XML mark-up language.

Although simple, this method does not profit from the extensibility ofthe MPEG7 standard.

It is also possible to extract from the description inserted in theservice document all the characteristics of the multimedia content.

At the extraction step E12 of the MPEG7 description, an MPEG7 documentis then generated possessing all the characteristics identified from thedescription of the WSDL document.

This method requires the creation of a tool for reading an MPEG7description and generating a specific MPEG7 document.

A third solution is based on an iterative method using the knownXML-Schema or Relax-NG validation tool. In practice, a first MPEG7document is extracted at the extraction step E12.

The comparison step E13 is adapted to validate this MPEG7 document fromthe description of the WSDL document.

If an error of the type “element X missing” appears, it is necessary toadd the characteristic X to the MPEG7 document.

The extraction step E12 is then reiterated in order to extract thecharacteristic X from the multimedia document and complete the MPEG7description.

The comparison E13 and extraction E12 steps are reiterated as long as anerror exists. Do   RES = Validation(document, schema)   If (RES does notcontain any error)    Test = 1   Otherwise    Test = −1   If (REScontains an error of the type ‘element X awaited’)     CAR =CharacteristicOf (X)     AddCharacteristic (CAR, document, X)     Test =0 As long as (Test = 0) If (Test = 1)    Validation successful Otherwise   Validation failed

It should be noted that many multimedia documents possess a binarycompressed MPEG7 description incorporated directly in this document.This MPEG7 description can be used as a base document for the validationmethod, in particular the iterative validation method described above.

This method of validating a multimedia content can be applied inparticular during the construction of the message.

Thus with reference to FIG. 2 a description will be given of a method ofproducing a request for a service offered by a server in a communicationnetwork, this service being described in a WSDL service descriptiondocument according to the invention.

A reading step E20 is first of all implemented in order to read thedescription document of a WSDL service.

An extraction step E21 is adapted to extract a first abstract part ofthe WSDL document adapted to describe a message exchanged over thecommunication network when an operation associated with the service isimplemented.

In practice, an operation is selected and the abstract descriptionassociated with this operation is extracted.

An extraction step E22 is adapted to extract the description of abstractconstraints associated with a binary multimedia document which is to beinserted in the message intended for the server.

A selection step E23 is then adapted to select a multimedia contentaccording to the description obtained at the extraction step E22.

In practice, a multimedia step is selected according to the abstractconstraints described in the WSDL service description document.

At the time of this selection of a multimedia content, the validationmethod described previously with reference to FIG. 1 can be implemented.

A test step E24 checks whether this selection has succeeded, that is tosay whether the multimedia document selected has been validated usingthe description of a multimedia content.

If not, a step E25 of generating an error intended for the client isimplemented.

Otherwise a step E26 of producing a request corresponding to the chosenoperation, intended for the server in the communication network, isimplemented.

This request includes the binary multimedia document selected at theselection step E23.

This request is next sent to a server for execution when the serviceoffered by this server is implemented.

Thus, when a message is constructed, the validation process makes itpossible to ensure that the image is valid, when an image is selectedfrom amongst several multimedia contents, or when a multimedia contentis produced.

A description will now be given with reference to FIG. 3 of thevalidation of a request received by the server in a communicationnetwork.

When the message is received, it is a question for the server or for anintermediate node between the client and the server on the communicationnetwork to ensure that the client has sent a multimedia document asspecified in the service description document according to theinvention.

This method of validating a request comprises first of all a step E30 ofreception of the request by a server, or by an intermediate node in thenetwork.

A validation step E31 is implemented using the content of the request.

This validation step E31 is identical to the validation method describedabove with reference to FIG. 1, in which the acquisition step E10consists here of extracting a multimedia document inserted in therequest.

A test step E32 checks whether the validation has succeeded.

If the validation has not succeeded, a step E33 of sending an errormessage is implemented, destined for the client.

If the validation has succeeded, a step E34 of executing this step isimplemented in a conventional manner on the server.

A step E35 of sending the results in the form of a response to theclient computer is then implemented.

The present invention thus makes it possible to describe in an abstractmanner multimedia contents in the context of Web services. It is thuspossible to constrain multimedia data which will be exchanged during theimplementation of a service, in a similar manner to that used forexchanging XML data.

In order to implement the methods of validating, producing a request fora service and executing a request for a service, devices associated withthese methods can be incorporated in a computer as illustrated in FIG.4.

In particular, the device for producing a request can be incorporated ina client computer C in a communication network whilst the device forexecuting a request can be incorporated in a server computer S in acommunication network.

Naturally the devices intended to implement the various methods of thepresent invention can be implemented in the same computer or indifferent stations in the communication network.

In particular, the device for validating a multimedia document willpreferably be incorporated both in a client computer C and in a servercomputer S in the communication network.

More precisely, the various means adapted to implement the steps of themethods according to the invention can be incorporated in amicroprocessor 100, a read only memory 101 (“Read-only memory” or ROM)being adapted to store a program for validating a multimedia document,producing a service request or executing such a request.

A random access memory 102 (“Random access memory” or RAM) is adapted tostore in registers the values modified during the running of the programfor validating a multimedia document, producing a service request orexecuting such a request.

The microprocessor 100 is integrated in a computer which can beconnected to various peripherals and to other computers in acommunication network 100. In particular, this computer corresponds to aserver computer S, a client computer C or an intermediate computer at anode in this communication network 10.

This computer S, C comprises in a known manner a communication interface110 connected to the communication network in order to receive ortransmit messages.

The computer also comprises document storage means, such as a hard disk106, or is adapted to cooperate by means of a disk drive 107 (floppydisks, compact disks or computer cards) with removal document storagemeans, such as disks 7. These fixed or removable storage means cancomprise the code of the methods according to the invention.

They are also adapted to store an electronic document describing aservice as defined by the present invention.

By way of variant, these programs can be stored in the read only memory101.

In a second variant, these programs can be received in order to bestored as described previously by means of the communication network 10.

The computer S, C also possesses a screen 103 for serving for example asan interface with an operator by means of the keyboard 104 or the mouse105 or any other means.

The central unit 100 (CPU) will then execute the programs relating tothe implementation of the invention. On powering up, the programs andmethods relating to the invention stored in a non-volatile memory, forexample the memory 101, are transferred into the memory 102, which willthen contain the executable code of the invention as well as thevariables necessary for implementing the invention.

The communication bus 112 affords communication between the varioussub-elements of the computer or connected to it.

The representation of this bus 112 is not limiting and in particular themicroprocessor 100 is able to communicate instructions to anysub-element directly or by means of another sub-element.

Naturally many modifications can be made to the example embodimentsdescribed above without departing from the scope of the invention.

1. A description document for a service offered by a server in acommunication network, comprising: a first abstract part adapted todescribe at least one message exchanged over the communication networkwhen the service is implemented; and a second concrete part adapted todescribe the information relating to the transmission of the messagesover the communication network, wherein said first abstract partcompries a description of abstract constraints associated with a binarymultimedia document.
 2. A service description document according toclaim 1, characterized in that said description of abstract constraintsis represented using the semantics of a description language of acontent of a binary multimedia document.
 3. A service descriptiondocument according to one of claims 1 to 2, characterized in that saiddescription of abstract constraints is represented using the semanticsdefined by the MPEG7 standard.
 4. A service description documentaccording to one of claims 1 to 2, characterized in that saiddescription of abstract constraints is represented in a mark-up languageof the XML type.
 5. A service description document according to one ofclaims 1 to 2, characterized in that said description of abstractconstraints is represented in a schema language such as XML-Schema orRelax-NG, tags being defined using the semantics of the MPEG7 standard.6. A service description document according to one of claims 1 to 2,characterized in that said description of abstract constraints isrepresented in a description language of a content of the multimediadocument, tags being adapted to integrate directly or by referenceattributes represented in a schema mark-up language such as XML-Schema.7. A service description document in accordance with claim 6,characterized in that the description language of a content of themultimedia document is defined according to the MPEG7 standard.
 8. Aservice description document according to one of claims 1 to 2,characterized in that said description of abstract constraints isrepresented in a schema language such as Schematron adapted to define aset of minimum constraints.
 9. A service description document accordingto one of claims 1, 2 and 7, characterized in that said description ofabstract constraints is inserted in a sub-part of said first abstractpart adapted to describe an abstract structure of the messagesexchanged.
 10. A service description document according to claim 9,characterized in that said first abstract part comprises a secondsub-part adapted to declare at least one elementary message pointing tosaid description of abstract constraints.
 11. A service descriptiondocument according to claim 10, characterized in that said elementarymessage is associated with an attribute adapted to specify that themessage comprises a binary multimedia content type.
 12. A method ofproducing a request for a service offered by a server in a communicationnetwork, the service being described in a service description documentaccording to one of claims 1, 2, 7, 10 and 11, characterized in that itcomprises the following steps: reading the description document of aservice; selecting a first abstract part adapted to describe at leastone message exchanged over the communication network when an operationassociated with the service is implemented; extracting a description ofabstract constraints associated with a binary multimedia document;selecting a binary multimedia document according to the description ofabstract constraints; and producing a request intended for the server inthe communication network including the binary multimedia documentselected.
 13. A method of validating a multimedia document when aservice offered by a server in a communication network is implemented,the service being associated with a service description document,characterized in that it comprises the following steps: acquiring themultimedia document; extracting a description of abstract constraintsassociated with a binary multimedia document from the descriptiondocument of a service; extracting a content description associated withthe multimedia document; and comparing the content description and thedescription of abstract constraints extracted from the servicedescription document.
 14. A method of validating according to claim 13,characterized in that the description of abstract constraints isrepresented in a language describing a content of a multimedia document.15. A method of validating according to one of claims 13 or 14,characterized in that the language describing a content of themultimedia document is defined under the MPEG7 standard.
 16. A method ofvalidating according to one of claims 13 to 14, characterized in that,at said extraction step, an MPEG7 description of the multimedia documentinserted in the multimedia document is extracted.
 17. A method ofvalidating according to one of claims 13 to 14, characterized in that itis implemented during a step of selecting a multimedia document to beinserted in message exchanged during the implementation of a serviceoffered by a server in the communication network.
 18. A method ofvalidating according to one of claims 13 to 14, characterized in that itis implemented during a step of validating a request received by aserver in a communication network for implementing a service describedin a service description document.
 19. A device for producing a requestfor a service offered by a server in a communication network, theservice being described in a service description document in accordancewith one of claims 1, 2, 7, 10 and 11, characterized in that itcomprises: means for reading said description document of a service;means for selecting a first abstract part adapted to describe at leastone message exchanged over the communication network when an operationassociated with the service is implemented; means for extracting adescription of abstract constraints associated with a binary multimediadocument; means for selecting a binary multimedia document according tothe description of abstract constraints; and means for producing arequest intended for the server in the communication network includingthe binary multimedia document selected.
 20. A device for producing arequest for a service in accordance with claim 19, characterized in thatit is incorporated in: a microprocessor; a read only memory adapted tostore a program for producing a request for a service; and a randomaccess memory comprising registers adapted to store the variablesmodified during the running of the program.
 21. A device for validatinga multimedia document during the implementation of a service offered bya server in a communication network, the service being associated with aservice description document, characterized in that it comprises: meansfor acquiring the multimedia document; means for extracting adescription of abstract constraints associated with the binarymultimedia document from the description document of a service; meansfor extracting a content description associated with the multimediadocument; and means for comparing the content description and thedescription of abstract constraints extracted from the servicedescription document.
 22. A device for validating a multimedia documentaccording to claim 21, characterized in that it is incorporated in: amicroprocessor; a read only memory adapted to store a program validatinga multimedia document; and a random access memory comprising registersadapted to store variables modified during the running of the program.23. A server computer in a communication network, characterized in thatit comprises means adapted to implement the validation method accordingto one of claims 13 to
 14. 24. A client computer in a communicationnetwork, characterized in that it comprises means adapted to implementthe validation method according to one of claims 13 to
 14. 25. A clientcomputer in a communication network, characterized in that it comprisesmeans adapted to implement the method of producing a request inaccordance with claim
 12. 26. A communication network, characterized inthat it comprises means adapted to implement the validation methodaccording to one of claims 13 to
 14. 27. A communication network,characterized in that it comprises means adapted to implement the methodof producing a request in accordance with claim
 12. 28. An informationstorage means, possibly totally or partially removable, which can beread by a computer system, comprising instructions for a computerprogram adapted to implement the method of validating a multimediadocument in accordance with one of claims 13 to 14, when this program isloaded in and run by the computer system.
 29. An information storagemeans, possibly totally or partially removable, which can be read by acomputer system, comprising instructions for a computer program adaptedto implement the method of producing a request according to claim 12,when this program is loaded in and run by the computer system.
 30. Acomputer program which can be read by a microprocessor, comprisingportions of software code adapted to implement the method of validatinga multimedia document according to one of claims 13 to 14, when thiscomputer program is loaded in and run by the microprocessor.
 31. Acomputer program which can be read by a microprocessor, comprisingportions of software code adapted to implement the method of producing amultimedia document according to claim 12, when this computer program isloaded in and run by the microprocessor.